The present invention relates to a device for use in connection with a motor vehicle provided with an internal combustion engine operated by pressure charging, the device affecting the charge-air pressure of the pressure charging unit in dependency on at least the rotary speed of the engine.
From the German publication DE-OS No. 31 29 686 (PCT No. 82/00140) a device of this kind is known in which the desired value of the charging air pressure is additionally adjustable in dependency on load conditions of the internal combustion engine.
For motor vehicles equipped with turbo charged engines, especially high output vehicles such as racing cars, it has been found that it is frequently very difficult in lower gears to accelerate the car without slippage of the driving wheels. This problem results not so much from the absolute magnitude of the torque but from the course of the torque versus rotary speeds. This relationship is illustrated in the diagram of FIG. 1 in which torque M is depicted in dependency on rotary speed for a suction engine (curve 1) and for a turbo charged engine (curve 2). The jump of torque occurring in a turbo charged engine particularly during a load change considerably impairs the controllability of the motor vehicle especially in taking curves.
Conventional designs for reducing slippage of drive wheels are based on the detection of a slip, for example by comparing rotary speed between driven and driving wheels of the motor vehicle. In order to reduce the slip either the ignition (for example in the DE-OS No. 23 22 368) or fuel mixing process (for example DE-OS No. 28 32 739) are controlled in order to reduce the torque applied to the driving axles.